linux-kernel - Re: [PATCH v10 4/9] cgroup: cgroup v2 freezer

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Message-ID: <20190424221034.GB22896@tower.DHCP.thefacebook.com>
Date:   Wed, 24 Apr 2019 22:10:39 +0000
From:   Roman Gushchin <guro@...com>
To:     Oleg Nesterov <oleg@...hat.com>
CC:     Roman Gushchin <guroan@...il.com>, Tejun Heo <tj@...nel.org>,
        Kernel Team <Kernel-team@...com>,
        "cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 4/9] cgroup: cgroup v2 freezer

On Wed, Apr 24, 2019 at 06:02:38PM +0200, Oleg Nesterov wrote:
> On 04/05, Roman Gushchin wrote:
> >
> > @@ -5830,6 +5926,12 @@ void cgroup_exit(struct task_struct *tsk)
> >  		spin_lock_irq(&css_set_lock);
> >  		css_set_move_task(tsk, cset, NULL, false);
> >  		cset->nr_tasks--;
> > +
> > +		if (unlikely(cgroup_task_frozen(tsk)))
> > +			cgroup_freezer_frozen_exit(tsk);
> > +		else if (unlikely(cgroup_task_freeze(tsk)))
> > +			cgroup_update_frozen(task_dfl_cgroup(tsk));
> > +

Hello, Oleg!

A good catch! It's actually a leftover from one of the previous versions
of the patchset. In the current iteration I'd replace it with:

	WARN_ON_ONCE(cgroup_task_frozen(tsk));

just to make sure we're not leaking the frozen bit.
Do you agree?

Thank you!

Roman